In order to understand the genetic background and dissemination mechanism of carbrpenem resistance and fosfomycin resistance in Enterobacteriaceae isolates, a clinical E. coli isolate HS102707 and an Enteobacter aerogenes isolate HS112625 which were resistant to both carbrpenem and fosfomycin, and positive in both blaKPC-2 and fosA3 were studied. Beside, a clinical Klebsiella pneumonia isolate HS092839 which was resistant to carbapenem was also studied. A 70-kb plasmid was successfully transferred to recipient E.coli J53 by conjugation test. PCR and southern blot showed blaKPC-2 was located on this plasmid. The complete sequence of pHS102707 showed this plasmid, belonged to the P11 subfamily (IncP1), has a replication gene, several plasmid stable genes, an intact IV secretion system gene cluster and a composite transposon Tn1721-Tn3 harbored blaKPC-2. Interestingly, a composite IS26 transposon carrying fosA3 was inserted in Tn1721-tnpA gene in pHS102707 and pHS112625, leading to the disruption of Tn1721-tnpA and the deletion of Tn1721-tnpR. However, only an IS26 with a truncated Tn21-tnpR was inserted in pHS092839 at the same position. To our best knowledge, this is the first report of fosA3 and blaKPC-2 co-located in the same Tn1721-Tn3-like composite transposon on a novel IncP group plasmid.